Convex To Make Flat Appear Flat

Hi All,

Is there a ‘formula’ to the slight convex to make a flat surface appear flat and not concave? (for example: the Parthenon or a Rolls Royce grill) Something like 1 degree of arc? Would a 'formula’ be different for different angles of intersection like a cube or pyramid?

I am very excited to hear from you as I have wanted to know this for years. I am a closeted inventor and industrial designer :\

Thank you for your consideration.


The design technique you refer to is called entasis. You are also correct, it is used on large structures like the Panthenon and small structures, like the grille of a Rolls Royce.

I did some google searching, but couldn’t find a very detailed description of applying the technique, however I did find it stated that in the greek buildings they would make the upper diameter of a column 83% that of the bottom. I would start there and tweak. Maybe you should also bring a ruler and tape measure to your local Rolls dealer?

If you do find out a definate technique, let us know. I for one would like to know.

In my classes we’re told to eyeball it. There is a formula to use when crowning molded plastic or cast metal parts, as they actually will sink more in the center and form a distinct dish shape. I don’t know for just aesthetic considerations, though.